© Organics Recycling Group Issued on 20/02/2013, Issue 1, Revision 1 Issued by JF, Approved by: KZ INFORMATION SHEET Composting - Noxious weeds 1. Introduction Compost producers aiming to produce a quality product will want to ensure that weed propagules have been destroyed and any toxins potentially contained in plant species have broken down through good practice composting and verification procedures. The PAS 100 Specification for composted materials1 requires that the number of weed seeds and propagules does not exceed zero germinating weed seeds and propagules per litre of compost. Propagules are seeds and other parts plants necessary for their reproduction. A noxious weed is ‘a plant species that has been designated as one that is injurious to agricultural and/or horticultural crops, natural habitats and/or ecosystems, and/or humans or livestock. Typically they are plants that grow aggressively, multiply quickly without natural controls (native herbivores, soil chemistry, etc.), and adversely affect native habitats, croplands, and/or are injurious to humans, native fauna, and livestock through contact or ingestion. Noxious weeds are a large problem in many parts of the world, greatly affecting areas of agriculture, forest management, nature reserves and parks, and other open space lands’2. Noxious weeds include: I. Poisonous weeds These are weeds that can cause illness, injury, or death to humans or animals. These include plants such as Ragwort (Senecio jacobae), Yew (Taxus baccata), Hemlock (Conium maculatum) and Rhododendron 1 British Standards Institution’s PAS100:2011 Specification for composted material 2 http://en.wikipedia.org/wiki/Noxious_weed 1 © Organics Recycling Group Issued on 20/02/2013, Issue 1, Revision 1 Issued by JF, Approved by: KZ (Rhododendron Ponticum) because they contain toxins which may be poisonous to living organisms. II. Invasive, non-native weeds Invasive, non-native weeds are plant species that have been introduced to a place where they do not naturally occur and started to cause problems. They have the ability to spread and transfer from gardens to farmland, upsetting the balance of the ecosystem. They can be characterised as having a very persistent growth form and method of reproduction. At the same time they have fewer natural predators, like pests or diseases, which results in resistance to control. Some examples of invasive, non-native species are: Japanese Knotweed (Fallopia japonica), Giant Hogweed (Heracleum mantegazzianum), and Himalayan Balsam (Impatiens glandulifera). Composting of noxious weeds In most cases destruction of weed propagules and breakdown of plant derived toxins occurs in composting heaps that reach and sustain thermophilic temperatures (55 to 75⁰C). It is crucial to ensure that adequate air and moisture conditions are maintained during the process. For composting systems that rely on turning/mixing (e.g. open air turned windrows), thorough mixing of each batch is essential to ensure that by the end of the process all material has been exposed to a high temperature for sufficient time. 2. Regulations and guidance Weeds Act 1959 The 1959 Weeds Act controls and tries to prevent the spreading of five injurious weeds to agricultural land. The supply of compost containing propagules from injurious weeds is likely to be viewed as an offence. Enforcement of the Weeds Act is carried out by Natural England on behalf of the Department of Environment, Food and Rural Affairs (Defra). It is not an 2 © Organics Recycling Group Issued on 20/02/2013, Issue 1, Revision 1 Issued by JF, Approved by: KZ offence to have these weeds growing on your land; however they must not be allowed to spread to agricultural land, particularly grazing areas or land which is used to produce conserved forage. Enforcement notices can be issued following complaints requiring landowners to take action to prevent the spread of these weeds. The Act identifies the following five injurious weeds: • Common ragwort, • Spear thistle, • Creeping (or field) thistle, • Curled dock, and • Broad-leaved dock. To aid their identification Defra’s website provides a leaflettitled ‘Identification of injurious weeds’ which describes each of the above injurious weeds. The leaflet can be downloaded from: http://www.defra.gov.uk/publications/files/pb4192-injurious-weeds.pdf For the same purpose, the Scottish Government has published Weed Guidance, which can be found at this link: http://www.scotland.gov.uk/Resource/Doc/915/0076371.pdf Ragwort Control Act 2003 and Defra’s Code of Practice on how to prevent the spread of ragwort The Ragwort Control Act amends the Weeds Act 1959. The Act provides for a code of practice to be prepared to give guidance on how to prevent the spread of ragwort. As a result, Defra released its Code of Practice on how to prevent the spread of ragwort, which can be downloaded from www.defra.gov.uk/publications/files/pb9840-cop-ragwort.pdf. The Scottish Government also released guidance on how to prevent the spread of ragwort (see http://www.scotland.gov.uk/Resource/Doc/228241/0061833.pdf). Further guidance on ragwort identification and the most appropriate means of controlling ragwort can be found in Defra’s Guidance on the disposal options 3 © Organics Recycling Group Issued on 20/02/2013, Issue 1, Revision 1 Issued by JF, Approved by: KZ for common ragwort (see http://www.defra.gov.uk/publications/files/pb11050- ragwort-dispose-110315.pdf). The Wildlife and Countryside Act 1981 This Act made it illegal to "plant or otherwise cause to grow in the wild’’ plants listed in Schedule 9, which specifies over 30 plants. They are usually invasive non-native species, which can reproduce vegetatively, i.e., from parts of the plant rather than by seeds. Therefore, incompletely composted parts of vegetation could re-grow in the compost or where the compost is used. The EC Habitats Directive The EC Habitats Directive requires European Union Member States to regulate the deliberate introduction of non-native species, so as not to prejudice native fauna and flora. The Conservation (Natural Habitats, &c.) Regulation 1994 transposed the Directive into national low. Environment Agency’s Knotweed Code of Practice The EA’s code has been written for anyone involved in the development and haulage industry who may encounter sites with Japanese Knotweed, or soil containing it. The code can be found at http://www.environment- agency.gov.uk/static/documents/Leisure/Knotweed_CoP.pdf. Further guidance: The EA’s web site provides detailed information on how to control and dispose of Japanese Knotweed at http://www.environment- agency.gov.uk/homeandleisure/wildlife/130079.aspx. The Scottish Government’s web site contains detailed guidance on control options for invasive, non-native species at http://www.scotland.gov.uk/Topics/farmingrural/SRDP/RuralPriorities/Options/ Controlofinvasivenon-nati. N.B.: The Scottish Government prohibits composting as a control option for Japanese Knotweed and Giant Hogweed. 4 © Organics Recycling Group Issued on 20/02/2013, Issue 1, Revision 1 Issued by JF, Approved by: KZ 3. Restrictions under the Compost Quality Protocol The latest version of the Compost Quality Protocol3 (the CQP) specifies that for inputs to composting, ‘The waste must not contain Japanese Knotweed’. Thus, composting processes certified to PAS 100 and the Compost Quality Protocol cannot accept any load containing Japanese Knotweed. 4. Poisonous weeds These are plant species which may be harmful or poisonous to humans, domesticated grazing animals, and wildlife. They include weeds which produce plant derived toxins like, grayanotoxin present in Rhododendron or coniine present in Hemlock. Common Ragwort – Senecio jacobaea Main toxin: pyrrolizidine alkaloids Ragwort is a native plant that naturally occurs on sand dunes but can be found along roadsides. It is controlled by the Ragwort Control Act 2003 and the guidance available (please see above) aims to prevent the spread of this plant and control its potentially negative impact on animals, especially on horses, which are particularly vulnerable. The following description of Common Ragwort is to help its identification. Plant characteristics o 30 – 90 cm high o Stem – tough and often tinged red near the base o Leaves – basal leaves forming a rosette o Seeds – 70 per flower can remain dormant for over 16 years when buried. o Flowers - yellow; 200 – 2,000 per plant 3 The Quality Protocol for the production and use of quality compost from source-segregated biodegradable waste, 2012 edition. 5 © Organics Recycling Group Issued on 20/02/2013, Issue 1, Revision 1 Issued by JF, Approved by: KZ Decomposition of toxin presents in Ragwort (pyrrolizidine alkaloids, also referred to as ‘PA’) Several research and development projects have been undertaken to establish the degradability of pyrrolizidine alkaloids. A first experiment showed a rapid decomposition of the toxin in ragwort stored in waste bags, from 340 mg/kg to less than 40 mg/kg in four weeks and virtually complete loss after 10 weeks4. Another study investigated the decomposition of pyrrolizidine alkaloids during composting, using a pilot-scale compost heap. The results showed that this toxin was completely degraded during the composting process5. Advice for disposal of Ragwort Small quantities of ragwort can be home composted. It may also acceptable to put ragwort in the council’s garden waste collection bin; prior to this using this disposal route, householders (by contacting their council) and local authorities should check whether the contracted composting operators can take ragwort. Some composters may have a policy to reject any load containing Ragwort and/or other poisonous weeds. According to Defra’s ‘Guidance on the disposal options for common ragwort’ and the Scottish Guidance on ragwort control, ‘composting of ragwort should only be carried out where British Standard PAS100 or equivalent can be met’. Rhododendron – Rhododendron Ponticum Main toxin: grayanotoxin Rhododendron is one of several poisonous plants commonly found in parks, gardens and the countryside of the UK.